Method of recovering carbon bisulphide



Patented July 1-, 1 930 um-:1) TATES .PATENTOFFICE onerenns J. srnosacxnn AND JAMES 1'. Joints, or MIDLAND, urcmonu, Assmuons TO THE DOW CHEMICAL CDMPANY, 0F MIDLAND, MICHIGAN, A .GOBPORATIOK 0]! MICH GAN 1E0 Drawing.

hydrogen in the charcoal. This hydrogen sulphide even after going through the condensers, which are employed to condensethe carbon bisulphide to liquid form, isnot condensed and carries with it considerable carbon bisulphide, the amount of the latter depending on the temperture to which the prodnets of the original reaction are subjected, and there will accordingly be a corresponding loss of carbon bisulphide. The object of the present invention is to eliminate this loss by bringing the hydrogen sulphide into contact with a suitable reagent whereby it is absorbed but the carbon bisulphide carried therewith is unacted upon.- Such carbon bisulphide may then be easily condensed.

To the accomplishment of the foregoing and related ends, the invention then consists of the steps hereinafter fully described and particularly pointed outin the claims, the following description setting forth but one of the various ways in which the principle of the invention may be carried out.

The preferred reagent which we employ to absorb the hydrogen sulphide in the manner hereinbefore indicated .is caustic soda (NaOH) because there are then produced by-products of considerable value, vii, sodium sulphide or sodium hydrogen sulphide, according to the following reaction, viz -(1) 2NaOH+H S=Na S+2H O;-

The caustic soda is employed in the form of a water solution, the strength of which may but preferably such solution will con sist of approximately 25 parts of caustic soda to approximately 75 parts of water.

After the hydrogen sulphide hasbeen thus absorbed, the residual carbon'bisulphide may be readily condensed in the usual manner, that is, providing such bisulphide is still in 7 Application filed January 25, 1938.; Seriai ms, 8331i.

the principalone of which is hy-- drogen sulphide gas due to the presence of METHOD OF RECOVERING CARBON BISIIDPHIDE the form of a vapor; If the absorbent caustic solution is notwarm enough to permit the carbon bisulphide to remain volatilized, it of necessity remains in such solution and will then be separated therefrom by distillation, or, if preferred, it can be drawn ofi as a liquid inasmuch as it isjnot soluble in such solution.

' Any hydroxide or carbonate with which hydrogen sulphide chemically react can be used to recover the carbon bisulphide in the manner hereinbefore described, and'the resultant loss of the bisulphide residuum, which has heretofore been burned with the other gaseous impurities resulting from the original reaction, is avoided.

It will be understood, oi course, that the present improved method'of recovering carbon bisulphide is not necessarily limited to the case where this compound is produced by tioned as the one generally or largely. employed for the production 0& such com pounds. In other words, of recovery is applicable to any process of manufacture of carbon bisulphide in which gaseous by-products, including hydrogen sulthe particular method hereinbefore menthe present method phide, result inasmuch as suchhydrogen sulphide will necessarily carry with it a certain amount of carbon bisulphide vapor.

While, the process has been described as one primarily for the recovery of carbon bisulphide, it may equally well be regarded as a process for the recovery, in the form of sodium sulphide or its equivalent, of the sulphur present as hydrogen sulphide in the exit gases. I g

'It may also be noted that instead of passing such. exit gases into a Water solution of caustic soda, they may be passed through a body of water and caustic soda subsequently added. The Water,'if sufficient in amount, will absorb substantially all of the hydrogen sulphide but has no such efle'ct on carbon bisulphide', and the addition of the caustic to the water, after it has absorbed 'a suflicient amount of the hydrogen sulphide will result ifn the formation of sodium sulphide, as beore. Still another satisfactory procedure ina distmctlyclaim as our 1nvent1on:

volving the use of a chemical absorbing agent and condensing such residual carbon bisulis to replace caustic soda with sodium su1- phlde.

hide inthe method as first described above.-

. Sign 11 other words, hydrogen sulphide ma be 1925- absorbed in sodium sulphide to form so iurn hydrogen sulphide and the latter is then subsequently treated with caustic soda to again form sodium sulphide which is used for further absorption of hydrogen sulphide The reactions occurring may be represented by the following equations, viz

(3) Na S H S =2NaHS; (4) NaHS +NaOH=Na S +H O.

In the foregoing modification of themeth od caustic soda is still used'in effect as the chemical absorbing agent, although not directly used in absorbing the hydrogen sulphide. Such modified form of procedure -1S specifically claimed in our copending aplication Serial No. 153,208, filed December Other modes of applying the dprinciple of I our invention may be employe instead of the one'explained, change being made as regards the process or method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed. I

We therefore particularly point out and 1. A process of making carbon bisulphide and an alkali metal sulphide. which comprises passing the vapor of sulphur in contact with from the carbon bisulphide thereby formed, subjecting the residual non-condensible gaseous mixture of carbon bisulphide and hydrogen sulphide to the action of an aqueous alkaline L solution toabsorb such hydrogen sulphide,

' ing the vapor of sulphur in contact with carthe action of an aqueous sodium hydroxide and separating therefrom such-residual car- ;bon bisulphide.

'2. A process of making carbon bisulphide and an alkali metal sulphide which comprises passing the vapor or sulphur in contact with carbon at ared heat, condensing from the reaction products a major portion of the ear -bon bisulphide thereby formed, subjecting the'residual non-condensible gaseous mixture of carbon bisulphide and hydrogen sulphide -to the action of an aqueous alkaline solution to absorb such hydrogen sulphide, and condensing such residual carbon bisulphide.

3. A process of making'carbon bisulphide and sodium sulphide which comprises passbon at a red heat, condensing from the read- 7 tion products a major portion of the carbon bisulphide thereby formed, subjecting the residual non-condensible gaseous mixture of carbon bisulphideoand. hydrogen sulphide to A solution to absorb such hydrogen sulphide,

ed by us this 30th day of December,

- CHARLES J. ISTROSACKER.

JAMES I. JONES. 

